Coded waveforms for optimised air-coupled ultrasonic nondestructive evaluation

摘要: This paper investigates various types of coded waveforms that could be used for air-coupled ultrasound, using a pulse compression approach to signal processing. These are needed because the low signal-to-noise ratios found in many ultrasonic nondestructive evaluation measurements, due large acoustic mismatch between air and solid materials. The waveforms, including both swept-frequency signals those with binary modulation, described, their performance presence noise is compared. It shown optimum choice modulation depends on bandwidth available type measurement being made.